The invention relates to an expandable pelletized material based on polyester, to moldable foams and foam moldings obtainable therefrom, to processes for producing these, and also to the use of the same as structural foam and/or insulation foam.
Foams based on polyester have a comparatively small range of applications, because of problems in process technology and because of densities that are usually high in comparison with polystyrene foams or with polyurethane foams.
Low-density polyester foams are known by way of example from U.S. Pat. No. 4,022,719. U.S. Pat. No. 5,256,702 describes extruded foam sheets based on a mixture made of polycarbonate and polyethylene terephthalate.
U.S. Pat. No. 5,158,985 discloses polycarbonate foams which were foamed via depressurization of a pelletized material in contact with CO2 under pressure.
Despite these advances, there remains a high level of demand for expandable pelletized polyester materials and polyester foams, where these exhibit not only low density but also good processibility. Moldable foams here feature extensive freedom in the shaping of the foam components, and provide a high level of resource conservation in use, since the density of the foam, and thus the amount of raw material required, and the properties of the foam, can be adjusted during the prefoaming process. These foam beads can then be foamed to give slabs or complex moldings in a single operation.